Difference between Tee and Barred Tee

Tee or Tee connection in piping engineering is a very important pipe fitting and is frequently used to combine or divide a flow. Two types of Tee are available, Equal Tee and Reducing Tee. However, in pigged pipelines, one special type of tee connection is widely used which is known as Barred Tee or Pigged Tee. In this article, we will try to study a few points about Barred Tee and Tee Connections.

Tee vs Barred Tee
Typical Tee and Barred Tee Connection

Tee vs Barred Tee

  • Tee is a type of fittings that allows fluid to flow on its main pipe and branch out. The branch can be designed equally the same size as the main pipe (known as Equal Tee), or smaller size than the main pipe (known as Reducing Tee).
  • Barred Tee is a special type of Tee that base from a normal tee (can be either equal tee or reducing tee) that at later stage, will be added with bar plates inside the branch outlet (From inside it looks like a steel cage) to restrict the pig from flowing from the header pipe into the branch pipes.

Design Codes and Standards for Tee and Barred Tee

  1. The international standard dimension of tee will be covered under ASME B16.9 or MSS-SP 75 (for DN16 and above). Click here to know more about Tee Connections.
  2. There is no international standard dimension for the barred tee. It is custom made using the ASME B16.9/ MSS-SP 75 tee as a base. However, many develop their barred tee based on Shell DEP 31.40.10.13-Gen or ISO 15590-2 standard.
  3. This design can be a guideline to assess Vendor’s design.
Reduced Barred Tee (Reference:  Shell DEP 31.40.10.13-Gen Figure 4)
Reduced Barred Tee (Reference: Shell DEP 31.40.10.13-Gen Figure 4)

Design Considerations for Barred Tee

  • The barred tee will be used when there is a requirement for pigging. Thus, many of its applications can be found in the pipeline or in the subsea field.
  • The bar plates that welded internally at the branch are to avoid the pig from changing direction or getting stuck at the branch outlet.
  • The design of the bar plates must be in sufficient quantity, thickness and adequately spaced to ensure the smoothness for the pig to run through the main pipe, and at the same time not affecting the flow that was meant to flow through the branch. Normal practice is to ensure that the opening in the branch pipeline after guided bars is not more than 40% of the main pipeline area.
  • The size of the bars in the branch connection has to be small enough not to restrict the flow but large enough to sustain the pressure of the flow.
  • To ensure the smoothness, the bar plates have to be a grind to suit the branch curvature. Any sharp edges, spatters and burs are required to be removed. This smoothness of the pigging process is important to protect the sensor of the pig from damage.
  • Refer to Shell DEP 31.40.10.13-Gen Figure 4 above; the quantity of the bar plates start with two (2) pieces and increase as the ID of the branch increase.
  • The bar plates ideally will be equally spaced.
  • For larger tee (size 14 inches and above), there will be a bridge plate in the middle to support the bar stiffness when getting hit by the pig.
  • The material of the bar plates commonly used the same as the tee material for weldability.
  • Standard practice is to avoid welding of guide bars directly on the high-stress concentrated areas of the extrusion neck. Bar ends must be machined to fit the branch.
  • Weld Repairs on Parent metal is prohibited.

Difference Between Tee and Barred Tee

So from the above discussion, we can summarize the following differences:

ParameterTeeBarred Tee
DefinitionStandard Pipe FittingA special type of piping component
ManufacturingGenerally by Extrusion or forgingMostly Fabricated
UseUsed in both piping and pipeline engineering used in pipeline engineering near the pig launcher/receiver
Design Code / Standard ASME B 16.9/MSS SP 75 Shell DEP 31.40.10.13-Gen or ISO 15590-2
Production QuantityLarge scale in bulkSelect small quantities (custom made)
CostCheaperCostlier than normal Tee

Few more references for you

Piping Design and Layout
Piping Materials
Piping Stress Analysis
Piping Interface

Reference

Nur Hidayah Haron

A Passionate Piping Engineer having extensive experience in the oil and gas field; mainly for topside piping system, subsea manifold and onshore LNG facilities. Familiar with codes and standards, i.e. American Petroleum Institute (API) standards, Petronas Technical Specification (PTS), Shell’s Design Engineering Practices (DEP), American Society of Mechanical Engineer (ASME), and American Society for Testing and Materials (ASTM), etc. To know more follow her on https://www.linkedin.com/in/nur-hidayah-haron-04881737/

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